Industrial systems commonly include multiple subsystems and components such as power motion devices (e.g., robots), maintenance access interfaces/points (e.g., gateboxes), operator access points (e.g., operator stations), etc., which can be arranged in one or more stations of the overall system to perform industrial processes. Industrial systems can be highly productive when operating properly, but also typically include hazards that have the potential to cause damage to equipment or product losses and to create safety risks. Such hazards can include, for example, motion-related hazards, thermal hazards, chemical hazards or radiation hazards. Consequently, it is desirable that industrial systems be operated properly and, in particular, that industrial systems be designed and operated in manners that reduce or limit the exposure of persons, equipment, products and the environment to such hazards.
For the above reasons, industrial systems often include precautionary or “safety” systems that control or guide the industrial systems to operate in manners that reduce the risks of equipment damage, product losses, and exposure of operators to safety hazards, that enhance the reliability of the industrial systems, and that assist in identifying the failures when they occur. Often, such safety systems are designed to continue to operate properly even with a system failure, such that the industrial systems (or at least the safety systems themselves) continue to operate in safety-enhanced modes.
To attain these goals of safety-enhancement, reliability, easy failure detection, and robustness of the safety systems in spite of failures, the safety systems employed in modern industrial systems often employ a variety of safety-related components. In particular, the safety systems commonly include safety-enhancing devices such as safety interlocks (e.g., emergency-stop buttons, light curtains, etc.). One or more such safety interlocks or other safety-enhancing devices can be implemented on the individual system components within the industrial system to form safety subsystems of the industrial system. Additionally, the safety systems often include complicated hardware controls (e.g., relay circuits) or software programs that are executed on system control devices, which control and monitor the operation of the safety systems.
Industrial systems often employ one or more standard industrial controllers such as programmable logic controllers (PLCs) to perform control, monitoring and diagnostic functions. While it is commonly the case that industrial systems include a central or main industrial controller that is in communication with other system components, other industrial systems employ multiple industrial controllers that can (but need not) be located within various system components, among which various functions are distributed. Regardless of their location within industrial systems, industrial controllers can be designed or programmed to perform specifically safety-related control and monitoring functions. The industrial controllers also can be in communication with one or more human/machine interfaces (HMIs) such as computer screens, by which safety-related and other status and operational information can be communicated to a human operator and by which the operator can provide commands to the system.
A typical industrial controller includes a microprocessor sequentially executing instructions of a control program stored in electronic memory to read and write control values to an input/output (I/O) table. The basic functions of the microprocessor in executing the control program and scanning the I/O table are performed by an operating system (OS) program. Industrial controllers can be programmed in a variety of computer languages, including “relay ladder language” or “ladder logic format” in which instructions are represented graphically by rungs composed of “normally-open” or “normally-closed” contacts connected in series or parallel to “coils” of relays (another computer language that can be employed, for example, is function block language). The contacts represent inputs from the controlled process and the coils represent outputs to the controlled process. This graphical language mirrors early industrial control systems which used actual relays to provide the control logic needed to control machinery or a factory.
Although industrial controllers are effective in providing reliability and safety, it is often difficult and costly to implement safety systems by way of industrial controllers within industrial systems. Industrial systems, and the stations within those systems, can vary significantly in terms of the numbers and types of system components and safety-enhancing devices, including safety subsystems and safety interlocks, that are employed. Given this variety in the features of industrial systems, the safety control programs for industrial controllers typically must be custom-written for the particular industrial systems within which the industrial controllers are intended to operate. This custom-writing of safety control programs can become expensive as new safety control programs are repeatedly written for new industrial systems.
Additionally, the safety control programs for the industrial controllers of an industrial system generally increase in complexity with the complexity of the industrial systems for which the control programs are intended, which depends upon (among other things) the number of safety-enhancing devices employed in the industrial systems and the number of different types of safety-enhancing devices that are employed. In particular, the safety control program(s) for a main industrial controller, which typically is in communication with all or most of the other components of an industrial system, can be particularly complicated to write so that proper control, monitoring, diagnostics, etc. of the industrial system and its safety-enhancing devices are performed and so that appropriate safety status information is made available to operators. The complexity of the safety control programs further exacerbates the costs associated with writing those programs and implementing safety systems using such programs.
Therefore, it would be advantageous if a new system could be developed, for implementation as part of an industrial system, for controlling and monitoring the components of the industrial system in a reliable, safety-enhanced manner, where the new system was relatively easy and inexpensive to implement. In particular, it would be advantageous if the new system was capable of being easily and inexpensively implemented in a variety of industrial systems having different numbers and types of safety-enhancing devices that are employed to manage or reduce the risks associated with various hazards such as motion-related hazards, thermal hazards, chemical hazards or radiation hazards. Further, it would be advantageous if the new system facilitated the communication of safety status information to operators and other systems and was capable of being implemented largely through the use of, and in conjunction with, standard components.